data modeling isys 464. start and login to oracle 10g exp to start:oracle popup menu –start...
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Data Modeling
ISYS 464
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Database Design Process
• Conceptual database design:– The process of creating a data model independent of
implementation details such as the target database model and physical considerations.
• Logical database design:– The process of designing database logical structure
based on a specific database model (such as relational model), but independent of a particular DBMS and physical considerations.
• Physical database design:– The process of implementing the database on a
secondary storage.
Requirements Collection and Analysis
• The process of collecting and analyzing information about the organization that is to be supported by the database system, and use this information to identify the requirements for the new system.
BART Tries Pay-By-Phone Systemhttp://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/01/30/BUPEUODJN.DTL&type=tech
• A contact-free cell phone payment program – puts a chip inside a phone, eliminating the need
for additional cards. – lets people pay by passing their phone over a
wireless reader.
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Making Airlines Reservations
• US Aiways -- http://www.usairways.com/awa/
• Select your seats
• Web check-In
FTD Florists Online
• http://www.ftdfloristsonline.com/index.html
Fact-Finding Techniques
• Examining documentation– Defining problem and need for database:
• Internal memos, minutes of meetings, documents that describe the problem, organizational chart
– Describe the current system:• Various types of flowcharts and diagrams, data dictionary,
database system design, program documentation
• Interviewing• Observing the enterprise in operation• Questionnaires
User Views
• A user view defines what is required of a database system in terms of the data to be held and transactions to be performed on the data from the perspective of a particular job role or enterprise application area.
• Identifying user views helps to ensure that no major users of the database are forgotten when developing the requirements for the new database system.
• Examples of user views:– Reports, Forms, documents
Conceptual Database Design Methodology
• Identify entity types.• Identity relationship types between the entity
types.• Identify and associate attributes with entity or
relationship types.• Determine attribute domains.• Determine candidate keys and primary key.• Validate conceptual model:
– Check for redundancy, support required transactions, review the model with user
Objectives of Database design
• Be able to link related records in the database.
• Eliminate data duplication.
Entity-Relationship Diagram
• ER modeling is a top-down approach to database design that begins by identifying the entities and relationships between entities that must be represented in the model.– Relative ease of use.
– Widespread CASE tool support.
– The belief that entities and relationships are natural modeling concepts in the real world.
– Classifying things according to their various kinds.
ERD Models Entities and Business Rules
• Example:– A customer may submit any number of orders.
However, each order must be submitted by exactly one customer.
– A student may register for a section of a course only if he or she has successfully completed the prerequisites for that course.
Entities
• An entity is a person, place, object, event, or concept in the user environment about which the organization wishes to maintain data.– Person: Employee, Student, patient– Place: Warehouse, Store– Object: Product, Machine.– Event: Registration, Sale, Renewal– Concept: Account, Course
• Physical existence:• Customer, student, product, etc.
• Conceptual existence:• Bank accounts, sale
Entity Type
• A collection of entities that share common properties or characteristics.
• An entity type represents a collection of entities.
• In an ERD, it is given a singular name.
• Diagrammatic representation:– A rectangle labeled with the name of the entity
Entity Instance
• An entity instance is a single occurrence of an entity type:– Student entity: SID, Sname, Major– Two instances of Student entity type:
• S1, Peter, Bus
• S5, Paul, Sci
Relationship Type
• Relationship: Interaction between entity types.– It is an association representing an interaction
among the instances of one or more entity types that is interest to the organization.
• It has a verb phrase name:– Faculty teach Course, Faculty advise Student– Customer open Account, Customer purchase
Product.
Figure 3-10 Relationship types and instances
a) Relationship type
b) Relationship instances
Binary Relationship
• A relationship involves two entity types.
• Three kinds of Binary Relationship - – 1:1– 1:M– M:M
• Determined by business rules
M:M Relationship
Peter
Paul
John
Woody
Alan
Mary
Linda
Nancy
Mia
Pia
A boy may date 0, 1, or many girls.
A girl may date 0, 1, or many boys.
Note: “Many boys date many girls” is not a correct interpretation.
Boy Girl
1:1 Relationship
Peter
Paul
John
Woody
Alan
Mary
Linda
Nancy
Mia
Pia
A man may marry 0 or 1 woman.
A woman may marry 0 or 1 man.
Man Woman
1:M Relationship
Peter
Paul
John
Woody
Alan
MaryBrianLindaAron
NancyRonald
MiaPia
A father has 1 or many children.
A child has 1 father.
Father Child
Cardinality Constraint
• A cardinality constraint specifies the number of instances of entity type A that can (or must) be associated with each instance of entity type B.
• Participation constraint– Full participation (Mandatory)– Partial participation (Optional)
Notations
Other Notations
UML Notations:– 0..1, 1..1– 0..*, 1..*– 3..5
• Traditional:
Student AccountHas1 1
Student AccountHas
1..11..1
1:1 Relationship
• Examples:– Husband, Wife– State, State Governor– Order, Invoice
1:M Relationship
• Examples:– Father, Child– Department, Employee– Customer, Order
M:M Relationship
• Examples:– Boy friend, Girl friend– Bank customer, Bank account– Student, Student organization
Traditional ERD Notations
Student Account
Faculty Course
Has1 1
EnrollM MAdvise
M
1
TeachM1
UML ERD Notations
Student Account
Faculty Course
Has1..11..1
Teach
1..*1..1
Enroll
0..* 0..*Advise
0..*
1..1
Book Notations
Student Account
Faculty Course
Has
Teach
Enroll
0..*Advise
Other Examples
• A database to record visitors and web pages they view.
• An online shopping website database to record customers, orders (shopping carts) and products purchased by customers.
• An auction database to record sellers and the items they sell, buyers and the items they purchase.
• BART Cell Phone Payment System.• Supermarket advertisement• Airline reservation• Florists Online
Recursive Relationship
• A relationship type where the same entity type participates more than once in different roles.
• Examples:– Employee – Supervise -- Employee– Student -- Tutor– Student– Faculty – Evaluate -- Faculty
Employee
Supervise
Supervisor
Superviswee
Employee
Supervise
M1
Attributes• Properties of an entity or a relationship.• Simple and composite attributes
– Address:Street address, City, State, ZipCode– Street Address: Number, Street, Apt#
• Single-valued and multi-valued attributes– Student’s Major attribute– Faculty’s DegreeEarned attribute– Vehicle’s Color attribute– Others: PhoneNumber, EmailAddress
• Derived attributes• Keys
– Candidate key, primary key, composite key
UML Notations
StudentSID {PK}Sname Fname LnameAddress Street City State ZipPhone[1..3]SexDateOfBirth/Age
SID {PK}Sname( Fname, Lname)Address( Street, City, State, Zip){Phone}SexDateOfBirth[Age]
Student
SID Sname
Fname Lname
Phone DateOfBirth
Age
Domains of Attributes
• The set of allowable values for one or more attributes.
• Input validation
• Examples:– Sex: F, M– EmpHourlyWage: Between 6 and 300– EmpName: 50 characters
Time-Dependent Attributes
• Auditing• Reconstructing the database state at a point in
time:– Database snapshot
• Regulations:– Sarbanes-Oxley
• Public Company Accounting Reform and Investor Protection Act of 2002 and commonly called SOX or SarbOx; July 30, 2002)
• Example:• ProductPrice: PID, {PriceHistory(Price,
TimeStamp)}
Attributes on Relationship Online Shopping Cart
Customer ShoppingCart
Product
Has
Has
1 M
M
M
CID CnameAddr CartID Date
PIDPname
Price
Order Form
Online Shopping Cart
Customer ShoppingCart
Product
Has
Has
1 M
M
M
CID CnameAddr CartID Date
Qty
PIDPname
Price
Attributes on Relationship
• Examples:– Student/Course: Grade– Order/Product: Quantity– Product/Country: Date, Quantity
Enroll
0..*0..*
Student
SID
Course
CID
Grade
Student CourseEnrollMM
Grade
Associative Entities• An entity–has attributes
• A relationship–links entities together
• When should a relationship with attributes instead be an associative entity? – All relationships for the associative entity should be many– The associative entity could have meaning independent of the other
entities– The associative entity preferably has a unique identifier, and should also
have other attributes– The associative entity may participate in other relationships other than the
entities of the associated relationship– Ternary relationships should be converted to associative entities
Figure 3-11a A binary relationship with an attribute
Here, the date completed attribute pertains specifically to the employee’s completion of a course…it is an attribute of the relationship
Figure 3-11b An associative entity (CERTIFICATE)
Associative entity is like a relationship with an attribute, but it is also considered to be an entity in its own right.
Note that the many-to-many cardinality between entities in Figure 3-11a has been replaced by two one-to-many relationships with the associative entity.
N-ary Relationship
• Doctor – Patient – Ailment
• Police – Crimal – Crime
• AirCraft – Bomb – Target
• Note: There is no deterministic relationship (1:1 or 1:M) between any two of these entities.
Figure 3-12 Examples of relationships of different degrees (cont.)
c) Ternary relationship
Note1: a relationship can have attributes of its own.Note2: This ternary relationship exists only if there is no binary relationship between these three entities.
Problems with ER ModelsConnection Traps
• Fan traps: Where a model represents a relationship between entity types, but the pathway between certain entity occurrences is ambiguous
Staff Division BranchHas Oversees
1..*1..1 1..11..*
Which branch does Peter work?
Division BranchOversees
1..*1..1Staff
Has
1..*1..1
Entity Type not System User or Organizational Unit
Report MeSendTo
MyCompany DepartmentHas
Note: An entity type represents a collection of entities.
Entities can be related to one another in more than one way
Figure 3-21 Examples of multiple relationships
a) Employees and departments
Example: Auction site: User and Auction Item